10.1021/ic501051q.s003
Paula Cucos
Paula
Cucos
Floriana Tuna
Floriana
Tuna
Lorenzo Sorace
Lorenzo
Sorace
Iulia Matei
Iulia
Matei
Catalin Maxim
Catalin
Maxim
Sergiu Shova
Sergiu
Shova
Ruxandra Gheorghe
Ruxandra
Gheorghe
Andrea Caneschi
Andrea
Caneschi
Mihaela Hillebrand
Mihaela
Hillebrand
Marius Andruh
Marius
Andruh
Magnetic
and Luminescent Binuclear Double-Stranded
Helicates
American Chemical Society
2014
temperature dependence
55 K
relaxation rate
Dynamic susceptibility measurements evidence
metal ions
helicate
Orbach mechanism
EPR spectroscopy
axis type anisotropy
dc field
Zn
fluorescence quantum yields
Co
exhibits fluorescence emission
tetrahedral geometry
M 2L
center
cobalt ions
helicand H 2L
2014-07-21 00:00:00
Dataset
https://acs.figshare.com/articles/dataset/Magnetic_and_Luminescent_Binuclear_Double_Stranded_Helicates/2272807
Three new binuclear helicates, [M<sub>2</sub>L<sub>2</sub>]·3DMF
(M = Co(II), <b>1</b>, Zn(II), <b>3</b>) and [Cu<sub>2</sub>L<sub>2</sub>]·DMF·0.4H<sub>2</sub>O (<b>2</b>),
have been assembled using the helicand H<sub>2</sub>L that results
from the 2:1 condensation reaction between <i>o</i>-vanillin
and 4,4′-diaminodiphenyl ether. The metal ions within the binuclear
helicates are tetracoordinated with a distorted tetrahedral geometry.
Direct current magnetic characterization and EPR spectroscopy of the
Co(II) derivative point to an easy axis type anisotropy for both Co(II)
centers, with a separation of at least 55 K between the two doublets.
Dynamic susceptibility measurements evidence slow relaxation of the
magnetization in an applied dc field. Since the distance between the
cobalt ions is quite large (11.59 Å), this is attributed in a
first instance to the intrinsic properties of each Co(II) center (single-ion
magnet behavior). However, the temperature dependence of the relaxation
rate and the absence of slow dynamics in the Zn(II)-doped sample suggest
that neither the simple Orbach mechanism nor Raman or direct processes
can account for the relaxation, and collective phenomena have to be
invoked for the observed behavior. Finally, due to the rigidization
of the two organic ligands upon coordination, the pure zinc derivative
exhibits fluorescence emission in solution, which was analyzed in
terms of fluorescence quantum yields and lifetimes.